1. Field of the Invention
The invention relates to an apparatus for the manufacture of mineral fibers from a drawable material, by centrifuging.
2. Related Art
Techniques are known, known as free centrifuging, in which material to be formed into fibers is fed in the molten state to the periphery of fiber-forming wheels and is entrained by these wheels until it becomes detached from them in the form of fibers under the effect of centrifugal force.
In these techniques, there are generally used three or four centrifuging wheels arranged close to one another. The molten material is poured onto a first wheel, is accelerated, and is then ejected onto the following wheel. The drawable material thus passes from one wheel to the other, each wheel transforming a part of the molten material into fibers and discharging the remainder onto the following wheel.
These techniques are especially used for the industrial production of rock wool from basaltic glasses, high furnace slags, or more generally any materials having a very high melting point.
Numerous improvements of these techniques have been proposed, such as that disclosed in European Patent Application No. 82400315.6.
The centrifuging wheels are subjected to high temperatures by reason of their contact with the molten material. These high temperatures should, however, not be such as to cause deformation and/or wear which will be detrimental to the longevity of these wheels. It is for this reason that the traditional apparatus described in the above mentioned European application includes cooling means formed by the circulation of water via the axle of the wheel and reaching the internal surface of the periphery of the wheel.
To convey the cooling water to the hub of the wheel a supply channel is preferably arranged within the axle and coaxially with it. This supply channel is fixed, and retained by sets of roller bearing in the axle of the wheel which is in rapid rotation relative thereto. These roller bearings are generally situated at the end of the channel, to the side of the wheel. Seals ensure the water tightness of the cooling circuit and protect these roller bearings.
The rotational velocity of the wheels being very high, the roller bearings retaining the supply channel are strongly acted upon, especially against the sealing joints. It is therefore difficult to protect them completely against normal operational conditions. Also these roller bearings wear very rapidly and must be replaced very frequently to avoid any seizing which would result in rupture of the supply channel.